Some additional questions regarding NG as a transitional fuel;

Where are the CNG passenger cars?
What about the supporting infrastructure?
How much to transport the gas?
How much to changeover the fleet and infrastructure?
Over what timeframe?
What is the new rate of NG depletion as demand ramps up?
What is it that we are “transitioning” to?
What happens to these plans after oil production peaks?

Mercury - to asnwer your question as to 'where are the CNG passenger cars' as I mentioned earlier, New Zealand has used CNG passenger cars.

Throughout the late 80s and early 90s this was the case, with CNG proving a viable alternative to the expensive petrol at the time. When the price of petrol fell, CNG was phased out.

CNG cars are not a new innovation. There is no reason why they can't be phased back in again.

"CNG cars are not a new innovation. There is no reason why they can't be phased back in again."

Not talking about innovation. Asking where are the CNG passenger vehicles rolling off the production lines in this country?

What about my other questions? When discussing transitioning from oil to NG other factors apart from just the existence of the technology have to be taken into account, otherwise the exercise is futile.

Mercury,
At present as I understand it natural gas is only used in a
limited way for transport. I notice Sydney busses have a number of
natural gas powered busses.

However the refineries here produce LPG from natural gas or crude oil.
That is widely used of course and the government gives a $2000 subsidy
to convert your car.

As I said earlier my son's father in law was managing director of the
major British bus manufacturer and he was on a UK government committee
studying other fuels. He answer to this is that with natural gas you
just cannot top up the tank, it has to be empty. The reason is that
a component of the gas increases in the proportion of gas in the tank
if you just keep topping it up.

Now our New Zealand correspondant says that NG was widely used in New Zealand
and without this problem.
Perhaps the gas in New Zealand was of a naturally different mix.
I will contact my son's father in law and ask him about it.
I will get back when I get an answer.

Bazz - it was indeed widely used in New Zealand. I don't know what problems were faced or how they were solved, but whatever the case, they must have been surmounted. (As for NZ correspondent, it's been some time since I lived there).

Mercury -

Of course there aren't many CNG passenger cars rolling off production lines now in this country.
The fact of the matter is however, CNG passenger technology exists - it's not a pipe dream.
To be fair, electrically powered vehicles such as the Tesla are showing great promise, however that technology is going to be expensive for some time yet.

But, I suppose it represents one possibility for what we are 'transitioning to.'

As for the logistics - of course these things are still being calculated. Obviously, we're not there yet, but if your plans are always based on whatever exists, I don't see how you can plan for the future.

If you've any other suggestions for a transitional fuel that's already proven capable of use, I'd like to hear it. As it stands, it's not a matter of having it 'already rolling off production lines' but getting to that stage. What's the alternative when we hit peak oil, if the electrical technology isn't yet affordable?

Gas is proven, it works. We don't have the infrastructure but we can work toward that on a limited scale, as gas isn't intended to be a permanent solution. The fact remains however - that switching to gas would be easier than the other options, and if this is something we need to do in a limited timeframe, as far as I can tell, it's our best option.

There is a small company in Sydney (Blade Electric Vehicle) who
convert Toyota and one other make to electric drive and supply the
converted car for about $20,000.

I saw one of his cars and very neatly done too.
He had a small trailer with a petrol generator and additional batteries
for interstate trips.

Toyota is reported as intending to release an electric version of
the Prius with a small petrol engine for backup purposes only.
Release ws aimed 2010 I think it was.